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Mic audio and TX power mods required with V6?


@KC2TAU
 

Hello,

I've recently purchased a V6 and was wondering if it's still recommended that one do the microphone audio mod that involves paralleling a 10 ohm resistor across R63 as well as the RF power equalization mod as described here: (https://groups.io/g/BITX20/topic/transmitter_mods/17458699?p=Created,,,20,1,80,0&jump=1)

I wanted to ask before I started modifications as perhaps one or both of the issues may have already been resolved on the V6 board.

Thank you,
- Mike


Stephen KO4CVU
 

Mike,

First let me tell you that I'm a newbie to ham radio, having earned my technician and general licenses in March of 2020. Bear this fact in mind as you read my comments.

I don't know about R63, there was a change made to R83 from 10 ohms to 2.2. ohms between v3 and v6. As far as audio level is concerned, I determined that the Baofeng microphone that was shipped with the uBITX was worthless and replaced it with a CB microphone with a built-in preamplifier (thanks to Evan's post). That improved things some. Then, I lifted one end of R86 and put a 33 uH inductor in series with it and I added 220 pF capacitors across R87 & R88. These changes really improved the power output on the 40 meter and 20 meter bands. (All of these modifications came from posts on the BIT20 group. I refer to them as "Howard's modifications.") In fact, I've made QSO's on both bands now after stringing up an EFHW antenna cut for 40 meters in the backyard.

I recommend that you have two important pieces of test equipment - a nanoVNA and a watt meter. I use the nanoVNA to check the VSWR of any antennas I try out. The power meter will help you evaluate the effectiveness of any changes you make. I'm not a big spender, so I bought the nanoVNA for about $100 on line and also found instructions to build a power meter. The screen on the nanoVNA I bought is small, BUT there's a free download that will let you display data on your laptop or PC and print it out to document your progress. I have no idea about how accurate my "poor boy's" watt meter is BUT I can make meaningful "before" and "after" modification comparisons ... and I can highly recommend "Howard's modification" to you. It doesn't come on the v6.

There are posts that discuss other modifications to the v6 that will improve power output on the higher frequencies at the expense of the lower frequencies. Right now, I am not ready to make that trade off.

One other very useful improvement that you will eventually want to make is installing Reed's software on the Arduino in your v6. I knew nothing about Arduinos and I was able to do it, so it isn't hard to do. Reed's software greatly improves the user friendliness of the v6. Among other things, it allows you to store 4 different favorite frequencies.

Rather that make this message any longer, I am going to stop now. If you want to know more about any of these topics, I will be happy to correspond with you on this board or on "the side" directly. Let me warn you though, there are a lot of folks in this group who know a lot more about the uBITX than I do. Most of my information comes second and third hand from them, and my "Elmer" whose real name is Bob.

73s

Stephen, KO4CVU


Evan Hand
 

Stephen,
Congratulations on your General Class ticket!

From the prior post, I would say you are well on your way to becoming an expert on the uBITX, as well as other aspects of the hobby.

Again, congratulations!
73
Evan
AC9TU


R. Tyson
 

I would agree that the nanoVNA is a great tool. I have just put up a new fan dipole for 40 and 30m. I trimmed the 40m section to resonance today and the nanoVNA made it very easy. I started of with the 40m antenna too long and snipped a bit off at a time to get it to resonance at the lower end of the band. Using the nanoVNA allowed me to check after each adjustment and I could see where the dip was and how much further I needed to trim back each leg of the dipole. The 40m dipole is now resonant where I want it, is very nearly 1:1 swr and a quick test 30 minutes ago with the uBitX showed I was being received all around Europe.     I wish they had been selling these 20 years ago it would have saved me a lot of time and effort when putting up new antennas. Just need to set up the 30m section of the fan dipole tomorrow.

Reg           G4NFR